On the contribution of the horizontal sea-bed displacements into the tsunami generation process

TL;DR

This paper investigates how horizontal sea-bed displacements, often neglected, contribute to tsunami generation by coupling detailed bottom motion reconstructions with a nonlinear water wave model, providing new insights into energy transfer during tsunamis.

Contribution

It introduces a methodology to incorporate horizontal displacements into tsunami modeling, highlighting their role in wave energy and generation, which was previously overlooked.

Findings

Horizontal displacements significantly influence tsunami energy balance.

The methodology successfully models the 2006 Java tsunami and recent events.

Horizontal motions contribute differently than vertical displacements to wave formation.

Abstract

The main reason for the generation of tsunamis is the deformation of the bottom of the ocean caused by an underwater earthquake. Usually, only the vertical bottom motion is taken into account while the horizontal co-seismic displacements are neglected in the absence of landslides. In the present study we propose a methodology based on the well-known Okada solution to reconstruct in more details all components of the bottom coseismic displacements. Then, the sea-bed motion is coupled with a three-dimensional weakly nonlinear water wave solver which allows us to simulate a tsunami wave generation. We pay special attention to the evolution of kinetic and potential energies of the resulting wave while the contribution of the horizontal displacements into wave energy balance is also quantified. Such contribution of horizontal displacements to the tsunami generation has not been discussed before, and it is different from the existing approaches. The methods proposed in this study are illustrated on the July 17, 2006 Java tsunami and some more recent events.